I don't have first hand experience. But from what I've read, the warning resets itself soon after the sensor realizes that the smaller "active" tank has enough DEF. Several people have reported having the sensor come on and go off by itself (e.g. ARD).

Note: the manual explains how an owner can top up the small tank DIY. So this is an 'approved' DIY maintenance item when you use the special BMW DEF filling bottle. OTOH I don't see how BMW could ever know whether you used Cummins or BMW DEF since it is a generic product.

Funf Dreisig

More great info! Thanks. The service advisor told me that a special tool would be needed for the indicator to be reset. I'm sensing a whole lot of HOT AIR from this service advisor and plan on moving up his chain of command if he doesn't call me back with the info I asked him for regarding how much DEF was actually used to refill the tanks....